|Publication number||US7749648 B2|
|Application number||US 11/234,062|
|Publication date||Jul 6, 2010|
|Filing date||Sep 22, 2005|
|Priority date||Sep 22, 2004|
|Also published as||CN1767228A, CN1767228B, US20060093905|
|Publication number||11234062, 234062, US 7749648 B2, US 7749648B2, US-B2-7749648, US7749648 B2, US7749648B2|
|Inventors||Joong Heon Kim|
|Original Assignee||Samsung Sdi Co., Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (6), Classifications (13), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims priority to and the benefit of Korean Patent Application No. 10-2004-0076134, filed on Sep. 22, 2004, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.
The present invention relates to a secondary battery, and more particularly, to a pouch for containing a secondary battery, to a secondary battery using the pouch, and to an apparatus for sealing the pouch.
Due to the wide use of portable electric products such as video cameras, mobile telephones, and portable PCs, secondary batteries, which can be used as the driving power sources of these portable electric products, have become increasingly important. This is because lithium secondary batteries have greater energy concentration per unit weight than other secondary batteries, such as conventional lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries. In addition, lithium secondary batteries can be rapidly charged. For all these reasons, use of lithium secondary batteries has significantly increased.
Lithium secondary batteries are classified according to the electrolyte used. Lithium ion batteries use liquid electrolytes, and lithium ion polymer batteries use solid polymer electrolytes. Lithium ion polymer batteries can use completely solid polymer electrolytes, which include no liquid electrolyte, or they may use gel type polymer electrolytes, which include some liquid electrolyte.
Lithium ion batteries, which use liquid electrolytes, can be contained in cylindrical or angular metal cans which are sealed by soldering. These can type secondary batteries have limitations on shape, restricting the design of electric products employing these batteries as power sources. Also, reducing the volume of the electric products is difficult with can type secondary batteries.
To address these limitations, pouch type secondary batteries in which two electrodes, a separator, and an electrolyte are contained in a sealed pouch comprising a film, have been developed as alternatives to can type secondary batteries.
As shown in
Pouch type secondary batteries are flexible and can take a variety of shapes, making it possible to manufacture secondary batteries having the same capacity, but having reduced volume and weight. However, unlike can type secondary batteries, the pouches used in pouch type secondary batteries are soft, making the pouch type secondary batteries weak, and decreasing the reliability of the pouch seal. Therefore, pouch type secondary batteries are mainly used with lithium ion polymer batteries using gel type or completely solid polymer electrolytes, rather than with lithium ion secondary batteries using liquid electrolytes, which may leak.
The electrode assembly is positioned in the pouch of the pouch type secondary battery such that a small pouch can have large capacity, as is needed for secondary batteries. Also, reduction of the area of the lip 23 surrounding the container 20 is desired since the lip 23 is not related to battery capacity or battery function. When the lip 23 is reduced, electrode assemblies having greater capacity can be contained in the pouch, resulting in secondary batteries having greater capacity. However, reduction of the lip 23 also reduces the reliability of the seal since the area to which the cover 10 is sealed to the container 20 is reduced.
However, during thermal fusion of the thermal adhesive polyolefin layer of the cover 10 to the thermal adhesive polyolefin layer of the container 20, a portion of the fused polyolefin layer seeps out of the pouch due to the external pressure applied during fusion. Such an occurrence adversely affects the external appearance of the pouch and reduces the thickness of the fused polyolefin layer, thereby reducing the reliability of the seal. Furthermore, enough of the polyolefin layer may seep out of the pouch during sealing to expose the metal barrier layer underneath the polyolefin layer. This occurrence causes a short circuit between the pouch and the electrode tabs.
The present invention is directed to a pouch for containing a secondary battery. The pouch prevents the resin layers of the pouch, in particular, the thermal adhesive layers from seeping out of the pouch during sealing by thermal fusion, which includes application of heat and pressure to the pouch. The pouch also improves the reliability of the seal despite a reduction in the sealing area of the pouch, and imparts increased battery capacity.
In another embodiment of the present invention, an apparatus for sealing the pouch is provided. The apparatus prevents at least some of the resin layers of the multi-layered pouch from deviating from their original positions during fusion. This apparatus prevents the metal barrier layer from becoming exposed, thereby preventing short circuits.
According to one embodiment of the present invention, a pouch for a secondary battery comprises a plurality of indentations in at least one of the lip of the container and the edge of the cover. Upon sealing, at least some of the indentations become filled with the resin of the thermal adhesive layers. The indentations can take the shapes of dots or lines and may be formed only on the sealing area or on the entire surface of the container and cover of the pouch, including the sealing area.
The indentations may be arranged on the cover and container of the pouch such that the indentations on the cover intersect the indentations on the container. Alternatively, the indentations on the cover correspond to the indentations on the container so that the resin of thermal adhesive layers forms an adhesive core.
In another embodiment of the present invention, a secondary battery comprises an electrode assembly having positive and negative electrodes separated by a separator. The electrodes and the separator are laminated to form the electrode assembly, which is contained in a pouch comprising two or more layers, forming a bare cell. Indentations are formed on at least one of the container of the pouch and the cover of the pouch and at least some of the indentations become filled with the resin of the thermal adhesive layers upon sealing the pouch.
In one embodiment, the indentations are formed on only one of the cover of the pouch and the container of the pouch, and a thick thermal adhesive layer is formed on the other of the cover and container of the pouch.
According to another embodiment of the present invention, an apparatus for sealing the pouch of a secondary battery comprises a sealing jig or sealing die that applies pressure to the sealing area of the pouch, thereby sealing the pouch. For example, one surface of the sealing jig contacts the top surface of the cover of the pouch, and another surface contacts the bottom surface of the lip of the container. The pouch is sealed by applying heat and pressure to the surfaces of the sealing jig. In one embodiment, the jig has at least one hole in each of its surfaces, such that upon applying pressure to the pouch, air is vented through the hole.
The above and other features and advantages of the present invention will become more apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:
Exemplary embodiments of the present invention will now be described in detail with reference to the attached drawings. Throughout the description, like reference numerals are used to identify like components in order to avoid repetitive descriptions of same or similar components.
In one embodiment of the present invention, a pouch 100 for containing an electrode assembly of a secondary battery comprises a container 120 and a cover 110. The container 120 comprises a cavity 121 for containing the electrode assembly and a lip 123. The cover 110 fits over the container 120 and has a portion that overlaps the lip 123 of the container. As shown in
The cavity 121 of the container 120 may be formed by pressing a multi-layer film. A gas chamber may be formed on the side of the cavity for removing gas generated by initial aging, charging and discharging. The indentations 117 in the sealing area may be formed separately from the formation of the cavity 121. Alternatively, the indentations 117 may be formed simultaneously with the cavity 121 by pressing, thereby reducing processing time and cost. The indentations 117 may take any suitable shape. For example, the indentations may be dot shaped, as shown in
As shown in
Electrode tabs 137 and 138 are attached to the anode 131 and cathode 135, respectively, and are spaced apart from each other by a predetermined distance. The electrode tabs electrically connect the electrode assembly to an outside source. Additionally, thermal adhesion tapes 139 may be attached to the portions of the electrode tabs 37 and 38 that overlap the lip 123 of the container 120 of the pouch. These tapes 139 enable better adhesion of the electrode tabs 139 to the pouch.
In one embodiment of the present embodiment, the pouch comprises three layers. However, it is understood that more layers may be provided. Also, the layers of the pouch may comprise materials different from those specifically described. For example, the cast polypropylene (CPP) thermal adhesive layer 115 may alternatively comprise a material selected from the group consisting of propylene chloride, polyethylene, ethylene propylene copolymers, copolymers of polyethylene and acrylic acid, and copolymers of polypropylene and acrylic acid.
The pouch comprises a nylon layer 111, a cast polypropylene layer 115 and an aluminum layer 113. The thickness of the entire pouch ranges from about 40 to about 120 micrometers. The nylon layer 111 and the CPP layer 115 each have a thickness ranging from about 10 to about 40 micrometers. The thickness of the aluminum layer 113 ranges from about 20 to about 100 micrometers.
In one embodiment, as shown in
Each indentation can have any suitable cross-sectional shape, for example a semi-circle or triangle, so that the indentations are easily formed. The width of each indentation may be equal to its depth. The depths of the indentations can be controlled by controlling the distance between the indentations and the temperature and pressure during thermal fusion. In addition, the temperature and pressure during thermal fusion can be controlled by controlling the distance between the indentations and the depth of the indentations. Controlling these variables is necessary to ensure that the thermal adhesive layer does not seep out of the pouch.
In sealing the pouch, a majority of the indentations 417 become filled with the portions of the thermal adhesive layer that deviates from its original position during application of heat and pressure. The thermal adhesive layers within the indentations are then cooled and hardened to form a hard seal.
As shown in
In one embodiment, at least one, and preferably a plurality of indentations 851 are formed on the areas of the first and second plates 850 a and 850 b which contact the sealing area of the pouch. Upon pressing, the nylon layers 811, metal barrier layers 813 and thermal adhesive layers 815 partially melt, become flexible and seep into the indentations 851 in the plates 850 a and 850 b of the sealing apparatus. As a result, portions of the pouch will be thicker than the rest of the layer. In particular, when the thermal adhesive layers 815 collect in the indentations 851 of the plates 850 a and 850 b, adhesive cores are created, thereby enforcing the pouch seal. The sealed pouches may have the external appearance shown in either
In another embodiment, shown in
According to one embodiment of the present invention, the thermal adhesive layers are formed in the indentations upon fusion and pressing of the thermal adhesive layers during sealing. This construction prevents the fused thermal adhesive layers from leaking out of the pouch, thereby improving adhesion. According to another embodiment of the present invention, the plates of the sealing apparatus comprise indentations for collecting the fused layers during sealing. This construction prevents the partially fused resins from leaking out of the pouch and prevents deterioration of the outer appearance of the pouch. Also, the partially collected fused resin improves the pouch seal. Accordingly, the pouches of the present invention improve the reliability of the pouch seal despite a reduction in the sealing area of the pouch, thereby increasing battery capacity.
Exemplary embodiments of the present invention have been described for illustrative purposes only. Those skilled in the art will appreciate that various modifications, additions and substitutions can be made without departing from the spirit and scope of the invention as disclosed in the accompanying claims.
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|U.S. Classification||429/175, 429/162, 429/176, 429/163|
|Cooperative Classification||H01M2/0287, H01M10/052, H01M2/0275, H01M2/021, H01M2/08|
|European Classification||H01M2/02E12, H01M2/08, H01M2/02B4B|
|Mar 19, 2008||AS||Assignment|
Owner name: SAMSUNG SDI CO., LTD., KOREA, REPUBLIC OF
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KIM, JOONG HEON;REEL/FRAME:020676/0366
Effective date: 20060925
|Nov 22, 2011||CC||Certificate of correction|
|Dec 24, 2013||FPAY||Fee payment|
Year of fee payment: 4